What is changing
GitHub will retire six AI models from all GitHub Copilot experiences on September 1, 2026 — four days from today. The announcement was posted to the GitHub Changelog on July 31, giving teams a 30-day notice window. The models being retired span Anthropic’s Claude 4.x line and Google’s Gemini 3.1 Pro. A seventh model, MAI-Code-1-Flash, follows on September 10. Any team relying on AI coding agents or Copilot-powered pipelines that reference a specific deprecated model by name will need to act before Monday.
This is not a soft migration: from September 1, the retired models will be completely unavailable in GitHub Copilot, including in the IDE extension, on Copilot.com, and in any Copilot Extension or workflow that calls the model API directly.
Which models are leaving
The six models being retired on September 1 are:
- Claude Opus 4.5 and Claude Opus 4.6 (Anthropic) — the high-capability Opus variants from earlier in 2026. Replaced by Claude Opus 5.
- Claude Sonnet 4.5 and Claude Sonnet 4.6 (Anthropic) — the mid-range Sonnet variants. Replaced by Claude Sonnet 5. Note: Sonnet 4.6 stays available for individual Copilot subscribers on annual plans; the retirement applies primarily to Business and Enterprise seat holders.
- Gemini 3.1 Pro (Google) — the Google multimodal model. Replaced by Gemini 3.6 Flash or Gemini 3.7 Flash.
- Raptor mini — Microsoft’s in-house small coding model. Replaced by MAI-Code-1.1-Flash, which GitHub added specifically ahead of these retirements.
Separately, MAI-Code-1-Flash (an earlier in-house Microsoft model) will retire on September 10, 2026. Teams can switch to MAI-Code-1.1-Flash, which launched in August as its direct successor.
Recommended replacements
GitHub’s supported model lineup after September 1 will include:
- Claude Opus 5 — for complex multi-step reasoning, large-context analysis, and agentic tasks requiring deep understanding.
- Claude Sonnet 5 — the default general-purpose coding model for most Copilot users post-transition; fast and capable for everyday code completion and chat.
- Gemini 3.6 Flash and Gemini 3.7 Flash — Google’s efficient multimodal variants, suited for tasks involving mixed-media context (code plus documentation images, diagrams).
- MAI-Code-1.1-Flash — Microsoft’s updated in-house coding model, successor to both Raptor mini and MAI-Code-1-Flash, optimised for speed on code completion tasks.
GitHub notes that newer models generally offer improved performance across coding, chat, and agent workflows relative to the models they replace. In most cases teams will not need to tune prompts heavily, but any workflow that relied on model-specific output formatting or behaviour should be tested against the replacement before the cutover.
What enterprise admins must do before September 1
For Copilot Enterprise and Business administrators, the retirement creates a practical action item: replacement models are not enabled automatically. Two categories of changes are needed:
1. Enable replacement models in Copilot settings. In your GitHub organisation, go to Settings → Copilot → Policies → Model access. Enable Claude Opus 5, Claude Sonnet 5, and whichever Google or Microsoft model fits your team’s workflow. Without this step, users who selected a retiring model as their default will find it unavailable on Monday morning with no automatic fallback.
2. Audit Copilot Extensions and CI pipelines for hardcoded model IDs. Any GitHub Action, GitHub Copilot Extension, or internal tool that calls the Copilot API with an explicit model parameter (e.g. model: claude-sonnet-4-6) will break silently or with an error after the retirement. Search your repositories for the deprecated model identifiers and update them to the supported alternatives.
Individual plan subscribers on annual billing do not need to take action for Sonnet 4.6 specifically — GitHub is preserving access to that model for this tier. However, they will lose access to Opus 4.5, Opus 4.6, Sonnet 4.5, Gemini 3.1 Pro, and Raptor mini along with everyone else.
What it means for dev teams
Three patterns to be aware of as Copilot’s model layer turns over:
Model churn is accelerating. GitHub has now retired more than a dozen Copilot models since January 2026 — GPT-5.2, GPT-4.1, Opus 4.6 Fast, Gemini 2.5 Pro, and now this batch. The practical implication for teams building developer tooling on top of Copilot is that model IDs should never be hardcoded. Treat the model parameter the same way you treat an API version header: configurable, externally managed, and auditable.
The performance step-up is real but workflow-breaking. Moving from Sonnet 4.6 to Sonnet 5 or from Opus 4.6 to Opus 5 typically improves code quality on complex tasks. But any prompt that was calibrated for the older model’s output style — response length, formatting conventions, reasoning depth — should be validated against the new one. A prompt that said “give me a 10-line summary” might now return a 3-line summary or a 30-line one depending on how the new model interprets the instruction.
GitHub Models itself retired last month. Teams that used the free GitHub Models API (a separate product for model access outside Copilot) should note that it was retired on July 30, 2026. The replacement path is through Azure AI or direct model-provider APIs. This is a separate change from the Copilot model retirements but compounds the planning burden for teams that used both.
Frequently asked questions
Which GitHub Copilot models are being retired on September 1, 2026?
GitHub is retiring six models from GitHub Copilot on September 1, 2026: Claude Opus 4.5, Claude Opus 4.6, Claude Sonnet 4.5, Claude Sonnet 4.6 (with an exception for individual annual-plan subscribers), Gemini 3.1 Pro, and Raptor mini. A seventh model, MAI-Code-1-Flash, follows on September 10, 2026.
What models replace the retired GitHub Copilot models?
GitHub’s recommended replacements are Claude Opus 5, Claude Sonnet 5, Gemini 3.6 Flash, Gemini 3.7 Flash, and MAI-Code-1.1-Flash. Enterprise admins must explicitly enable these in their Copilot model policy settings before September 1 or users will lose access to those AI capabilities.
What do enterprise Copilot admins need to do before September 1?
Enterprise and Business Copilot administrators must go to Settings → Copilot → Policies → Model access and enable the replacement models before September 1, 2026. Any Copilot extensions or CI workflows that reference a deprecated model by ID must also be updated to use a supported model identifier.
Is Claude Sonnet 4.6 being retired for all Copilot users?
Not universally. Individual GitHub Copilot subscribers on annual plans retain access to Claude Sonnet 4.6 beyond September 1. The retirement applies to Copilot Business and Enterprise plan users and to monthly individual plan subscribers. Check your plan type in GitHub settings to confirm whether the change affects you.
Sources
GitHub Changelog — Upcoming August 2026 model deprecations in GitHub Copilot (July 31, 2026)
GitHub Roadmap — Issue #1308: GitHub Copilot August 2026 model deprecations (official tracking)
AI News Bank — GitHub Copilot adds MAI-Code-1.1-Flash ahead of September model retirement (August 2026)